Method for sealing evacuated vessels



July 24,1934. R. MMZIMBER ,9

' METHOD FOR SEALING EVACUATED VESSELS Filed on. 9.1950

fl m hjm INVENTOR BY W -f ATTORNEY- Patented July 24, 1934 METHOD me some mucus-rep VESSELS Raymond MQZimber, Bloomfield, N. 1., assignor, by mesne assignments, to Radio Corporationof America, a corporation of Delaware Application mm 9, 1930, Serial No. mass a Claims. (01. 494) This invention relates to sealing methods and apparatus, and with particularity to such methods as are used in the manufacture of lamps, audions and vacuum tubes in general.

An object of the invention is to provide a novel method of tipping-off lamps, audions and similar devices.

In the art of manufacturing electron discharge devices, lamps and similar devices, the usual practice heretofore has been to subject the so-called exhaust tubulation to the heat of a tipping-oil torch to fuse or render plastic-the walls of the exhaust tubulation. Subsequent to this softenin the tubulation is subjected to a pull to separate the completed device from the unused length of the exhaust tubulation. It has been found that this method in many cases produced defective seals, particularly where the exhaust tubulation is of considerable internal diameter or of very thin-walled glass tubing. Accordingly it is another object of the present invention to provide a method of separating a completely exhausted device such asa lam}: or audion from the tubulation without subjecting the tubulation to a longitudinal pull. In accordance with thisobject it is proposed to employ a novel type of tipping-01f torch wherein the flame itself acts both to fuse the wall of the exhaust tubulation and at the same time to act as a cutter for severing the fused tubulation.

Another feature ofthe invention relates to th method of sealing off exhaust tubulations of relatively large internal diameter or thin-walled tube by employing in successiona relatively wide heating flame and subsequently a tapered and intense cutting flame. 4

Other features and advantages not specifically enumerated will be apparent after a consideration ofthe following detail description and the ap- 40 pended claims.

Referring to the drawin8 Figs. 1, 2 show one method of tipping-0R or sealing according to the invention;

Figs. 3, 4 show another method of sealing according to the invention;

Figs. 5,6 and 7 show the preferred manner of sealing or tipping-off; and 1"lg.8showsthetypeofsealortipordinarily producedby prior art methods. Referring more particularly to Figs. 1 to 4, the numeral 1 represents a length of tubing such as glass or .other fusible material which is to be severed into separate lengths" with the ends of each length hermetically sealed. Tubes of. this nature are employed in manyarts, and it is inbeen thoroughly completed, the lamp or audion is tended that the scope of the invention comprises the application of the novel method to all these arts.

However, the invention exhibits outstanding advantages in. the art of manufacturing lamps, audions and similar devices wherein the tubulation 1 is usually provided with a narrow tube re-- ferred to in the art as an exhaust tubulation. This tubulation is of course carried by the lamp or audion and has its open end connected through a suitable coupling to the evacuating pump as indicated schematically by the numeral 2. At the proper stage in the manufacture of the lamp or audion, namely when the exhaustion thereof has moved, in the case of an automatic machine, to bring the tubulation 1' into alignment with a tipping-off torch 3, which may comprise a pair of gas burners adapted to be positioned on opposite sides of the tubulation 1. Theseburners may be of any known construction for using any suitable kind of gas. The common practice is to employ fire jets having a relatively broad fire edge, and when the tubulation once becomes plastic and collapses it is subjected to a longitudinal pull to separate the collapsed portions. Due to this method of sealing off it has been found upon close examination that a great number of seals are defective principally due to the fact that any pulling on the tubulation while it is being subjected to the heat causes the formation of air pockets and unequal strains on-the walls of the sealed portion.

In accordance with the present invention it is proposed to effect the sealing or tipping oil. in twov separate steps without exerting any mechanical pull on the tubulation. Thus as shown in Fig. 1, a pair of burners 3 are employed, preferably so designed as to provide fiat wedge shaped fire jets 4. The burners- 3 may be mounted in any convenient manner to enable them to be rotated through an angle of approximately During the normal position of the burners the edges of the wedge shaped fire jets are parallel to the axis of the tubulation 1, thus causing the tubulation to'be subjected to heat through a comparatively wide area. After the tubulation becomes plastic and collapses to the position shown in Fig. 2, the burners 3 are rotated by any suitable mechanism (not shown) through an angle of 90 to bring the wedge shaped edges of the fire jets 4 perpendicular to the tubulation 1, in which position the said fire jets act as cutting 'jets and completely sever the previously collapsed portions of the tubulation 1. It will be understood 110.

pioyed in this second or cutting off stage if dc-- sired. -Instead of employing a pair of burners of course that a higher temperature may be emthat are turned through an'an'gle to effect the initial collapsing and final cutting operations, the

same eflect may be achieved by employing apair of. burners 5 having sharp or wedge shaped flames 6'positioned with the edge of the flame perpendicular to the tubulation. The said burners are so mounted that they may be oscillated in a vertical direction to the positions indicated in dotted lines in Fig. 4. Thus the burners -in oscillating collapse the tubulation 1 throughout a considerable portion of its length in thesame manner that the burners 3 of 1 effect a collapsing. After the tubulation 1 is thus collapsed the burners 5 are held stationary at approximately the central part of the collapsed portion of the tubu- --lation, and if desired, althouglrnot necessarily,

the temperature of the jets 6 m ay be increased to effect the cutting operation.

Instead of employing oscillating or rotatable jets, it is preferred to employ twoseparate jets.

For example, as shown in Fig. 5, the tubulation 1 I is first subjected to a pair of relatively broadjets- '1. It will be understood of course that during this sealing off process that the vacuum within the device acts upon the tubulation to draw the fused portion thereof inwardly, as indicated by the numeral 12, thus providing a very solid seal both on the inner and outer ends of the tip.

It is precisely because of this suction within the device that the prior art methods of tippingo'if-produce non-uniform seals and consequent increased shrinkage. The action of the prior methods of tipping-oil are schematically illustrated in Fig. 8, wherein it will be seen that due to the vacuum within the tubulation the soft tip 13 tends .to be sucked in, thus providing a sealing surface which is not much larger than the thickness of the wall of the tubulation. Not only is this type I of seal ineflicient, but it is also mechanically weak.

However, seals produced by the methods dis-- closed in Figs. 1 to '7, namely using an initial broad flame' to collapse the tubulation over a 1,907,008 v relatively large area and then a sharp cutting flame produce strong and highly emcient seals. It will be understood, of course, that in the method illustrated in Figs. 5, 6 and '1 that the temperature of the initial jets 7 is so regulated as to just collapse the walls of the tubulation in the manner shown in Fig. 6, andthat the temperature of the jets 10 is sufliciently high'to act as a cutting flame for the collapsed walls.

While separate burners are shown in Figs. 6

and 7 for effecting the successive steps, it willbe understood that a single pair of burners may be employed and suitable means associated with the burners for converting the relativelybroad jets 7 into a tapered Jet 10.

It will be understood that the drawing merely shows illustratively, certain preferred manners of practicing the invention, and itis intended that the invention is' not to be limited thereto, since in its broad aspect the method of sealing or tipping off is applicable to any art wherein mechanically strong and eiflci t seals are required, whether the same be of gl material.

-What is claimed is:

l. The method of sealingand severing a glass tube which comprises heating said tube without exerting a pull thereon intermediate its endsby a relatively broad flame to collapsethe-wali of said tube, then heating the collapsed walls by a separate sharp intense cutting. flame, and simultaneously subjecting said tube to exhaustion to produce a seal between the collapsed walls having a sealing surface much greater than the cross sectional area of the tube wall. I

2. The method of severing a glass tube an sealing the severed ends without exerting any pull thereon including applying a heating flame over a substantial'length of the tube at the point to be severed until the glass wall of the tube softens and collapseaand then concentrating the flame at the center of the softened area to melt through the tuhe to sever and seal'the severed ends.

3. The method of severing and-sealing a glass tuberin whicha vacuum is maintained without exerting any pull on the tube including the steps of applying a plurality of gas flames to the tube to heat a substantial area of the tube so that it collapses and the softened walls contact and then concentrating the gas flames to alimited area to melt-the tube through.

R. IL

or other fusible III 

